MIAMI (Reuters) - Carnival Corp (>> Carnival Corp) has won U.S. approval to operate culturally-themed cruises to Cuba and plans to start taking travelers there in May, joining a growing list of maritime companies hoping to profit from a thaw in relations between Washington and Havana.

The United States and Cuba have been working for months to improve relations after more than five decades of animosity that led to a trade embargo against the communist-led country.

The countries formally agreed last week to restore diplomatic relations on July 20.

Miami-based Carnival, the world's largest cruise operator, said it was still in talks with Cuba for approval to start specialized humanitarian and cultural visits there that fall within U.S. embargo guidelines.

Americans are still banned from going to Cuba as tourists but are allowed to go there for a dozen approved motives such as visiting family or participating in academic, professional, religious or educational programs.

Carnival is the first major U.S.-based cruise ship company to venture into Cuban waters. Two other Miami-based companies, Royal Caribbean Cruises Ltd (>> Royal Caribbean Cruises Ltd) and Norwegian Cruise Line Holdings Ltd (>> Norwegian Cruise Line Holdings Ltd), have expressed interest in Cuba but say the U.S. embargo remains an obstacle.

Frank Del Rio, the Cuban-born president and chief executive officer of Norwegian, said Carnival's move took the island one step closer towards an overall easing of leisure travel

"I extend my congratulations and best wishes to Carnival for pioneering this critical first step," he said.

Swiss company, MSC Cruises, last week became the first cruise line to base a ship in Cuba, announcing that the 2,120-passenger MSC Opera will take up winter residence in Havana from December to April, in partnership with a Cuban state-owned travel firm.

In May the U.S. Treasury Department approved several licenses for passenger ferry services between the United States and Cuba.

Such services were cut off in the 1960s, following the Cuban revolution that brought Fidel Castro to power.

Also last week, the U.S. Treasury Department issued a license authorizing a Palm Beach luxury yacht company, Paul Madden Associates, to provide charter services to Cuba.

Madden told Reuters his company has upwards of 50 vessels available ranging from 75-feet, all the way up to 250-feet mega-yachts capable of transporting 18 passengers.

Carnival said its cruise license was approved by the U.S. Department of the Treasury and the U.S. Department of Commerce and would be launched in May under its new "fathom" brand, set up last month to run cruises with humanitarian and cultural themes to the Dominican Republic.

Carnival will use the 710-passenger vessel, the MV Adonia, for its Cuba cruises, on the small side for the company, whose ships typically carry 2,000 to 3,000 people.

Carnival said the cruises would focus on education, the environment and economic development and feature Spanish lessons and workshops on the country's heritage. There will be no casinos or stage shows.

The Cuba cruises will start at $2,990 per person excluding taxes and other fees. They will be more expensive than typical regional cruises because of visa costs, paperwork, and the fact that the U.S. rules require passengers on cruises to Cuba to spend at least 8 hours a day on the ground and participating in academic, professional, religious or educational programs.

Carnival shares were up 0.84 percent at $50.20 in late afternoon trading on the New York Stock Exchange.

(Reporting by David Adams in Miami and Ramkumar Iyer in Bengaluru; Editing by Saumyadeb Chakrabarty, Christian Plumb and Andrew Hay)

By David Adams